iphone unavailable/erase offline/device with me.

Greetings alawfaq, 

You are correct that if you have removed the device from your iCloud account you can no longer take any remote actions, as the device is no longer connected to your account. 

If you have the device with you and it is showing unavailable on the display, what you’ll need to do is connect it to a computer and restore the software. This article goes over the steps you’ll need to take - If you forgot your iPhone passcode Though we’ve pulled the steps out of the article for you, there are some screenshots you may have find helpful within the article. 

Step 1: Make sure that you have a computer (Mac or PC)

This process requires a Mac or PC. If you're using a PC, make sure that it has Windows 10 or later, and that iTunes is installed. You also need the cable that came with your iPhone, or another compatible cable, to connect your iPhone to the computer.

If you don't have a computer and you can't borrow one, you need to go to an Apple Retail Store or Apple Authorized Service Provider for help.

Step 2: Turn off your iPhone

1. Unplug your iPhone from the computer if it’s connected.

2. Turn off your iPhone using the method for your iPhone model:

• iPhone 8, iPhone 8 Plus, iPhone X and later, including iPhone SE (2nd and 3rd generation): Press and hold both the side button and the Volume down button until the power off slider appears.

• iPhone 7, iPhone 7 Plus, iPhone 6s, and iPhone 6: Press and hold the side button until the power off slider appears.

• iPhone SE (1st generation), iPhone 5s, and earlier: Press and hold the top button until the power off slider appears.

3. Drag the slider to turn off your iPhone, then wait a minute to make sure that it turns off completely.

Step 3: Put your iPhone in recovery mode

1. Get ready by finding the button on your iPhone that you'll need to hold in the next step:

• iPhone 8, iPhone 8 Plus, iPhone X and later, including iPhone SE (2nd and 3rd generation) use the side button.

• iPhone 7 and iPhone 7 Plus use the Volume down button.

• iPhone SE (1st generation), and iPhone 6s and earlier use the Home button.

2. Press and hold the correct button for your iPhone while immediately connecting your iPhone to the computer. Don't let go of the button.

3. Keep holding the button until you see the recovery mode screen on your iPhone, then let go.

Step 4: Restore your iPhone

1. Locate your iPhone in the Finder or in iTunes on the computer that it’s connected to. (Learn how to find your connected iPhone.)

2. Choose Restore when you see the option to Restore or Update. Your computer downloads software for your iPhone and begins the restore process. If the download takes more than 15 minutes and your device exits the recovery mode screen, let the download finish, then turn off your iPhone and start again.

3. Wait for the process to finish. 

4. Disconnect your iPhone from the computer, then set up and use your iPhone. 

Thanks.